Endoscope apparatus

Abstract

There is provided an endoscope apparatus capable of stably and precisely measuring a distance to an object by suppressing variations in measured values of the distance to the object depending on the presence or absence of pigment dispersion or the like and capable of enabling observations based on clear and high quality images. The endoscope apparatus includes an optical system that condenses light from an object and simultaneously forms two optical images having the same characteristics with difference only in focal point; an imaging element that captures the two optical images formed by the optical system and acquires two images; and a calculation unit that obtains distance information corresponding to a distance to the object based on a contrast ratio of the two images in a range in which the two images acquired by the imaging element have a common contrast.

The invention claimed is: 
     
       1. An endoscope apparatus comprising:
 an optical system that forms two optical images having different distances to a focal point in focus of an object; 
 an imaging element that acquires two images by capturing the two optical images; and 
 a calculation unit that obtains distance information corresponding to a distance to the object based on a value which is obtained by a comparison process which compares a contrast value of one of the two images and a contrast value of the other of the two images, the comparison process being performed in a distance range in which the two images have a common contrast. 
 
     
     
       2. The endoscope apparatus according to  claim 1 , wherein the two optical images formed by the optical system have the same optical characteristics. 
     
     
       3. The endoscope apparatus according to  claim 1 , wherein the calculation unit stores a map associating the value with distance information and obtains the distance information from the map using the value. 
     
     
       4. The endoscope apparatus according to  claim 1 , wherein the two optical images formed by the optical system overlap in a distance range of 10% or more of a modulation transfer function in a frequency corresponding to a maximum resolution. 
     
     
       5. The endoscope apparatus according to  claim 1 , comprising
 an image synthesizing unit that generates a composite image by adopting pixel information having a higher contrast from the two images acquired by the imaging element; and 
 a display unit that displays both the composite image generated by the image synthesizing unit and the distance information obtained by the calculation unit. 
 
     
     
       6. The endoscope apparatus according to  claim 5 , comprising a characteristics processing unit that performs a process of varying display characteristics of both images on at least one of the two images acquired by the imaging element, wherein
 the image synthesizing unit synthesizes the two images after going through the process provided by the characteristics processing unit; and 
 the display unit displays both the composite image generated by the image synthesizing unit and the distance information at a boundary position between the two images. 
 
     
     
       7. The endoscope apparatus according to  claim 1 , wherein
 the optical system comprises a light condensing optical system that condenses a light beam from the object and a branching optical system that branches the light beam condensed by the light condensing optical system; and 
 the imaging element is disposed at a different position from a branch point by the branching optical system in an optical axis direction. 
 
     
     
       8. The endoscope apparatus according to  claim 1 , wherein the imaging element captures the two images simultaneously.